The White House's top lawyer has decided to resign in order to return to private practice.

White House counsel Greg Craig will leave his post in January. He will be replaced by Bob Bauer, a longtime adviser to President Barack Obama.

Craig had been the subject of repeated questions from Washington political insiders since last summer. They were pondering his future in the administration after he led the president's initiative to close the Guantanamo Bay military prison by January.

Those questions were answered when the White House announced his departure on Friday. Craig becomes the highest-ranking official so far in the Obama administration to resign.

"It has been a busy first year, and I feel very lucky to have been a part of it," Craig wrote in his resignation letter to Obama.

Obama issued a statement praising Craig as a trusted adviser who took on numerous difficult challenges. He was involved in the selection and confirmation of Supreme Court Justice Sonia Sotomayor.

"I'm indebted to Greg not only for leading the counsel's office but for his many decades of service to this country as well. He has been a huge asset in the White House, and he will be missed," the president said. "I will continue to call on him for advice in the years ahead."

White House press secretary Robert Gibbs said Craig's departure was not due to any dissatisfaction with his handling of Guantanamo policy. It was common knowledge that Craig told Obama after he was appointed that he didn't want to serve in the counsel role for more than a year.